1. Field of the Invention
The present invention relates to a method of controlling reception in a data broadcast receiver which receives a data broadcast of which data is transmitted in a frame comprising a plurality of packets and is interleaved at a same bit position in each packet and transmitted. The invention also relates to a method of broadcasting data to such receivers.
2. Description of the Related Art
A TV data broadcast system for enabling reception of a terrestrial data broadcast is currently being examined in Japan. The system allows data reception by mobile receivers and uses data signal subcarriers 4.5 fH and 7.5 fH (fH=15.73 kHz, the horizontal synchronizing pulse frequency) within a sound signal band of a television signal as the transmission path. The terrestrial data broadcast system provides programs such as:
Electronic mail service;
News, such as, newspapers, magazines, TV programs and others;
Vacancy information of concerts, movies, restaurants, hotels and others;
Information on time schedules, delays and vacancies of trains or buses;
Information on traffic jam, parking zones, gas stations, toilets, car shops and others;
Information on public facilities, hospitals, travel bureaus and others;
Information on shopping, such as, bargain sales and others;
Information on recreation and pleasures, such as, horse races, bicycle races and others;
Finance information, such as, stock prices and others;
Software, such as, MIDI data, games and others;
So-called narrow cast targeting on limited people in groups, companies, schools and others;
Information about disasters, such as, earthquakes, tidal waves, fires and others;
Play-by-play broadcasting of sports and others; and
Radio calling (pager).
However, the programs are not restricted to the above, and it can be considered that the programs will be further diversified in the future.
In the TV data broadcast system, the data is transmitted in the form of frames. One such a frame is shown in FIG. 1. The frame consists of total 9232 bits, including a 16-bit framing code or frame-sync (FC) and 32 data packets each having 288 bits. One data packet is made up of a 16-bit mode control (MC), a 14-bit prefix (PF), 176-bit service data (DAT) and a check code bit (CHC) for correcting errors.
In the TV data broadcast system, the data of all packets in the frame are interleaved with a depth of 32 in the vertical direction, as shown by the dashed arrow 20 in FIG. 1. That is, after transmitting the frame-sync signal FC, the most significant bit of the MC in the first packet is sent first, then the most significant bit of the MC of the second packet, etc. In the same manner, the second bit in the MC of the first packet is transmitted after the most significant bit of the MC in the 32nd packet. It is therefore necessary to receive all the data of the frame to which respective packets belong in order to decode the data of each packet.
The 16-bit MC comprises five significant information bits and eleven error correction bits. FIG. 2 shows the information bits b1-b5 of the MC currently defined in the TV data broadcast system, b1 being the most significant bit. Five broadcast services are defined at present.
In some of the above-mentioned data broadcast programs, the program broadcasting time or reception enabled time is restricted. Operation of the receiver in the time other than the rogram broadcast time greatly consumes power, thereby leading to disadvantages in the receiver for mobile reception, in particular. Manually operating the receiver is a troublesome operation.
It is an object of the present invention to provide, in the above-mentioned data broadcast, when receiving a program whose broadcasting time or reception enabled times is restricted, a method for controlling reception of a data broadcast receiver which can automatically minimize the ON time of the receiver for receiving the program.
To this end, according to a first aspect of the invention, a method for controlling reception in a data broadcast receiver which receives a data broadcast of which data is transmitted in a frame form consisting of a frame identification portion and a plurality of packets each consisting of at least a data portion and a broadcast identification portion transmitted prior to the data portion and of which data, except for that of the frame identification portion, is interleaved at a same bit position of each packet and transmitted, is characterized in that,
under control of a control device, operations of the receiver are:
detecting a frame identification portion of a frame;
deinterleaving and decoding data in a broadcast identification portion when the frame synchronization has been acquired;
deinterleaving and decoding program identification data and time information data of reception control information included in a data portion when the decoded broadcast identification portion data has an identifier for identifying a reception control information broadcast;
entering a standby mode until the time specified from the time information data based on the decoded predetermined program identification data and the associated time information data; and
entering a reception enabled mode when the specified time has come.
A second aspect of the invention is characterized in that the program identification data consists of program number data, service number data, broadcasting station identification data and/or broadcasting channel data, and the time information data consists of transmission time data, retransmission time data and/or intermittent transmission data.
A third aspect of the invention is characterized in that reception control of the receiver is carried out by gradually receiving the reception control information broadcast based on the category of program.
A fourth aspect of the invention is characterized in that if the receiver has identified the broadcast identification portion including an identifier of a time signal broadcast in a reception enabled mode, the receiver calibrates the time of an internal clock by using time information included in the data portion of the associated packet.
A fifth aspect of the invention is characterized in that the receiver again enters the reception enabled mode slightly earlier than the specified time.